In fact, the show paid tribute to victims of Naval Yard shooting a few seasons back: "In honor of the Men and Women who lost their lives or were injured at the Washington Naval Yard on 9/16/2013"
In September 2013, Aaron Alexis, the lone gunman who was also a civilian contractor suffering from mental health issues, entered the Washington Naval Yard (former headquarters of NCIS), and went on a shooting spree killing several people in the process till he was shot dead himself by disparate members of the law enforcement community.
The REACT team, was initially called Rapid Emergency Reaction Counter Threat Team but then changed to Regional Enforcement Action Capabilities Team, NCIS's version of SWAT, was formed as a direct result, nearly two months after Aaron Alexis killing spree. Its primary purpose is to combat active shooter scenarios. The program was instituted by NCIS Director Andrew Traver.
The REACT team is based out of USMC Camp Pendleton (San Diego), and have ready access to long guns, armor, radios and emergency vehicles, and are specifically trained in active-shooter scenarios.
This show aired several months before the 2018 All-Star Game which was held in Nationals Park, which is seen (albeit geographically inconsistent) in several rooftop scenes. A billboard for that game is shown in the final scene with Gibbs on the rooftop reading Ducky's novel.